Compact vertical inductors extending in vertical planes

ABSTRACT

A device includes a substrate, and a vertical inductor over the substrate. The vertical inductor includes a plurality of parts formed of metal, wherein each of the parts extends in one of a plurality of planes perpendicular to a major surface of the substrate. Metal lines interconnect neighboring ones of the plurality of parts of the vertical inductor.

This application is a divisional application of U.S. patent applicationSer. No. 15/419,894, filed Jan. 30, 2017, entitled “Compact VerticalInductors Extending in Vertical Planes,” which is a continuationapplication of U.S. patent application Ser. No. 13/091,440, filed Apr.21, 2011, now U.S. Pat. No. 9,559,053, entitled “Compact VerticalInductors Extending in Vertical Planes,” each application isincorporated herein in its entirety.

BACKGROUND

Inductors are essential devices in many integrated circuits, such asradio-frequency (RF) circuits. It is often required that the inductorshave high inductance values. This requirement, however, is difficult toachieve on integrated circuits because high inductance needs to beachieved with the cost of high chip area usage.

To improve the inductance of inductors, three-dimensional inductors weredeveloped, wherein an inductor may be formed in a plurality of metallayers to form a helical shape, and the portions of the inductors indifferent metal layers are interconnected. The further improvement ofthe inductors, however, is still limited, for example, due to theincreasingly smaller distances between metal layers and the respectivesemiconductor substrate, the requirement for forming dummy patterns, andthe undesirable Eddy currents in the semiconductor substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the embodiments, and the advantagesthereof, reference is now made to the following descriptions taken inconjunction with the accompanying drawings, in which:

FIG. 1 illustrates a perspective view of a vertical helical inductor inaccordance with an embodiment;

FIGS. 2 through 3D are cross-sectional views of the vertical helicalinductor in FIG. 1;

FIG. 4 illustrates a perspective view of a vertical inductor inaccordance with an alternative embodiment;

FIGS. 5A through 5D are cross-sectional views of the vertical inductorin FIG. 4; and

FIG. 6 illustrates a perspective view of a vertical inductor formed oftwo mirrored portions, wherein each of the portions has the structureshown in FIGS. 4 through 5D.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the embodiments of the disclosure are discussedin detail below. It should be appreciated, however, that the embodimentsprovide many applicable inventive concepts that can be embodied in awide variety of specific contexts. The specific embodiments discussedare merely illustrative, and do not limit the scope of the disclosure.

A vertical inductor is provided in accordance with an embodiment. Thevariations of the embodiment are then discussed. Throughout the variousviews and illustrative embodiments, like reference numbers are used todesignate like elements.

FIG. 1 illustrates a perspective view of inductor 20 in accordance withan embodiment. Inductor 20 includes ports 22 and 24. A current (notshown) injected into port 22 thus may flow to port 24, and vice versa.Inductor 20 is formed over substrate 26, which may be a semiconductorsubstrate such as a silicon substrate, a dielectric substrate, or thelike. In the illustrated exemplary embodiment, inductor 20 includesparts P1 through P4, which are interconnected through metal lines. Inalternative embodiments, inductor 20 may include more or fewer parts.

FIG. 2 illustrates a cross-sectional view of the structure shown in FIG.1, wherein the cross-sectional view is obtained from the plane crossingline 2-2 in FIG. 1. Inductor 20 includes portions formed in a pluralityof metal layers, which is shown as M1 (the bottom metal layer in therespective die/wafer) through Mtop (the top metal layer in therespective die/wafer) in the illustrated exemplary embodiment. It isnoted, however, that inductor 20 may or may not include portions inbottom metal layer M1 and/or top metal layer Mtop.

As shown in FIG. 2, inductor parts P1 through P4 are separated from eachother by dielectric regions 34, wherein each of dielectric regions 34includes portions in a plurality of dielectric layers, in which metallayers M1 through Mtop are formed. Part P1 is connected to part P2through metal line 36. Part P2 is connected to part P3 through metalline 38. Part P3 is connected to part P4 through metal line 40. In anembodiment, metal lines 36, 38, and 40 are in different metal layers,although they can be formed in same metal layers. Metal lines 36, 38,and 40 are illustrated using dashed line since they may be in planesdifferent from the illustrated plane. The lengthwise directions of metallines 36, 38, and 40 are parallel to major surface 26A of substrate 26.

FIGS. 3A through 3D are cross-sectional views of the structure shown inFIG. 1, wherein the cross-sectional views are obtained in the verticalplanes crossing lines 3A-3A, 3B-3B, 3C-3C, and 3D-3D, respectively, inFIG. 1. Referring to FIG. 3A, assuming current I1 flows from port 22 toport 24, then starting from port 22, metal lines/pads 100 and vias 102form a spiral metal feature spinning from outer side to inner side(please refer to arrow 106), until metal line 36 is reached.

As shown FIGS. 3A and 3B, through metal line 36 (also refer to FIG. 2),part P1 of inductor 20 is connected to part P2. Similarly, starting frommetal line 36, metal lines 100 and vias 102 form a spiral metal featurespinning from the inner side to the outer side (please refer to arrow108), until metal line 38 is reached. Through metal line 38 (also referto FIG. 2), part P2 of inductor 20 is connected to part P3, as shown inFIGS. 3B and 3C. In an embodiment, metal line 38 may act as the centertab, wherein an electrical connection can be made to center tab 38.

Referring to FIG. 3C, starting from metal line 38, metal lines 100 andvias 102 form a spiral metal feature spinning from the outer side to theinner side (please refer to arrow 110, assuming current I1 is injected),until metal line 40 is reached. Through metal line 40 (also refer toFIG. 2), part P3 of inductor 20 is connected to part P4, as shown inFIG. 3D. Again, in FIG. 3D, starting from metal line 40, metal lines 100and vias 102 form a spiral metal feature spinning from the inner side tothe outer side (please refer to arrow 112), until port 24 is reached.

In FIGS. 3A through 3D, the spiral metal features are formed of metallines/pads 100 and vias 102. Each of the spiral metal features maycomprise an outer metal feature having a rectangular shape, with a metalline 100 in a top layer of inductor 20 and a metal line 100 in a bottomlayer of inductor 20 forming two sides of the rectangle, and columns 104(FIG. 3A, for example), which are further formed of metal lines/pads 100and vias 102, forming the other two sides of the rectangle. Therectangle has a break, so that it does not form a loop. Furthermore, toform the spiral shape, addition metal lines 100 and vias 102 are formedinside and connected to the rectangle.

Assuming current I1 (FIGS. 3A and 3D) is injected from port 22 and flowsto port 24, current I1 flows in the counter-clockwise directions106/108/110/112 in inductor parts P1 through P4. Conversely, if currentI1 flows from port 24 to port 22, then current I1 flows in thecounter-clockwise direction in each of parts P1 through P4. Each ofparts P1 through P4 extends in a vertical plane that is perpendicular tomajor surface 26A of substrate 26, wherein the vertical planes are shownas planes Plane 1 through Plane 4 in FIG. 2. Accordingly, inductor 20 isreferred to as a vertical helical inductor. Furthermore, assuming axis44 (also refer to FIGS. 1 through 3D) is an axis of the spiral metalfeatures, then axis 44 extends in the direction parallel to the majorsurface 26A of substrate 26.

FIGS. 4 through 5D illustrate inductor 20 in accordance with analternative embodiment. Unless specified otherwise, the referencenumerals in these embodiments represent like elements in the embodimentsillustrated in FIGS. 1 through 3D. This embodiment is similar to theembodiment as in FIGS. 1 through 3D, except that in each of inductorparts P1 through P4, instead of forming spiral metal features, metalconnections form a single near-ring structure, which may have arectangular shape, except there is a break in the near-ring structure.Each of inductor parts P1 through P4 extends in a vertical plane that isperpendicular to major surface 26A of substrate 26. Accordingly,inductor 20 as shown in FIGS. 4 through 5D is referred to as a verticalinductor. Parts P1 through P4 are interconnected to form a coil, whereinaxis 44 of the coil extends in a direction parallel to major surface 26Aof substrate 26.

FIGS. 5A through 5D are cross-sectional views of the structure shown inFIG. 4, wherein the cross-sectional views are obtained in the planescrossing lines 5A-5A, 5B-5B, 5C-5C, and 5D-5D, respectively, in FIG. 4.Referring to FIG. 5A, port 22 is electrically coupled to metal line 100in a top metal layer of inductor 20. Metal column 104, which is alsoformed of metal lines/pads 100 and vias 102, connects port 22 to metalline 100 in a bottom layer of inductor 20. Through another metal column104, the connection traverses back to metal line 100 that is in the samemetal layer as port 22. Through metal line 36, part P1 of inductor 20 isconnected to part P2, as shown in FIG. 5B.

Referring to FIG. 5B, in part P2, metal line 36 is electrically coupledto metal line 100 in the bottom layer of inductor 20, and the connectiontraverses to metal line 38 in the top layer of inductor 20. Throughmetal line 38, part P2 of inductor 20 is connected to part P3, as shownin FIG. 5C.

As shown in FIG. 5C, in part P3, metal line 38 is electrically coupledto metal line 100 in the bottom layer of inductor 20 through column 104,which is further coupled to metal line 40 through another metal column104 and the metal line 100 in the top layer of inductor 20. Throughmetal line 40, part P3 of inductor 20 is connected to part P4, as shownin FIG. 5D, wherein metal line 40 is further electrically coupled toport 24 through metal lines 100 in the top layer and the bottom layer ofinductor 20, and through metal columns 104. It is observed that ifcurrent I2 is injected into port 22, current I2 flows in acounter-clockwise direction in each of parts P1 through P4, until itflows to port 24. Conversely, if a current is injected into port 24, thecurrent will flow in the clockwise direction in each of parts P1 throughP4.

Comparing FIGS. 3A through 3D with FIGS. 5A through 5D, it is observedthat all FIGS. 3A through 3D and FIGS. 5A through 5D may include thenear-ring structures in the parts of the respective inductors. Thenear-ring structures are formed of the metal lines in the top layer andthe bottom metal layer of inductor 20 and the metal columnstherebetween. Furthermore, as shown in FIGS. 3A through 3D and 5Athrough 5D, each of inductor parts P1 through P4 may include arectangular metal feature including two metal lines forming two sides ofthe rectangle, and metal columns 104 forming the other two sides of therectangle.

The inductor 20 as shown in FIG. 4 is an asymmetric inductor, in whichports 22 and 24 extends in different directions. FIG. 6 illustrates aperspective view of symmetric inductor 120, which includes inductors 50and 52 interconnected to form inductor 120. The structure of inductor 50may be essentially the same as the inductor 20 shown in FIG. 4. Thestructure of inductor 52 may, or may not, be mirrored from inductor 50.Inductor 52 may have axis 44′, which is parallel to axis 44 of inductor50, and parallel to major surface 26A of substrate 26. Metal line 54interconnects inductor portions 50 and 52. In the embodiments a centertab is needed, metal line 54 may act as center tab, with metal line 56connected to metal line 54.

By forming vertical inductors, the inductance density may be improvedover that of conventional spiral inductors whose planes (in which therespective turns/semi-turns are located) are parallel to the majorsurfaces of the respective semiconductor substrates. Simulation resultsrevealed that in a chip area of 50×100 μm², an inductor with aninductance of about 0.6 nH can be achieved if the embodiment shown inFIG. 1 is adopted. If the embodiments in FIGS. 4 and 6 are adopted, thenthe inductance values may be as high as about 0.45 nH (in a chip area of50×100 μm²) and about 0.9 nH (in a chip area of 100×100 μm²),respectively. As a comparison, to achieve about 0.6 nH, a conventionalspiral inductor needs about 50×200 μm². Therefore, the embodiments haveimproved inductance density. It is appreciated that the inductancedensity may have values slightly different from the above-presentedresults, depending on the routing.

Simulation results also indicated that the Q value of the embodimentshown in FIG. 1 is about 7. Therefore, the structure shown in FIG. 1 hasa high inductance value and a moderate Q value, and is suitable forhigh-frequency applications. If higher Q values are needed, theembodiments in FIGS. 4 and 6 may be adopted, wherein the respective Qvalues may reach about 16 to 17.

In accordance with embodiments, a device includes a substrate, and avertical inductor over the substrate. The vertical inductor includes aplurality of parts formed of metal, wherein each of the parts extends inone of a plurality of planes perpendicular to a major surface of thesubstrate. Metal lines interconnect neighboring ones of the plurality ofparts of the vertical inductor.

In accordance with other embodiments, a device includes a substrate; aplurality of metal layers over the substrate; and a vertical inductor.The vertical includes a plurality of parts formed of metal; and a spiralmetal feature in each of the plurality of parts. The spiral metalfeature comprises a plurality of metal lines in the plurality of metallayers and a plurality of vias interconnecting the plurality of metallines. The spiral metal feature extends along a vertical planeperpendicular to a major surface of the substrate. Metal linesinterconnect the plurality of parts.

In accordance with yet other embodiments, a device includes a substrate,and a vertical inductor over the substrate. The vertical inductorincludes a coil formed of metal, with an axis of the coil extending in adirection parallel to a major surface of the substrate.

Although the embodiments and their advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the embodiments as defined by the appended claims. Moreover,the scope of the present application is not intended to be limited tothe particular embodiments of the process, machine, manufacture, andcomposition of matter, means, methods and steps described in thespecification. As one of ordinary skill in the art will readilyappreciate from the disclosure, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed, that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the disclosure.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps. In addition, each claim constitutes a separateembodiment, and the combination of various claims and embodiments arewithin the scope of the disclosure.

What is claimed is:
 1. An inductor comprising: a first inductor, the first inductor comprising: a first spiral pattern about a first axis, the first axis being parallel to a major surface of a substrate, wherein the first spiral pattern comprises: a first spiral feature in a first plane over a substrate; a second spiral feature in a second plane over the substrate; and a third spiral feature in a third plane over the substrate, each of the first plane, the second plane, and the third plane being perpendicular to a major surface of the substrate, wherein each of the first spiral feature and the second spiral feature comprises a first metal line and a second metal line discontinuous from the first metal line, the first metal line extending continuously between adjacent spiral features of the first spiral feature, the second spiral feature, and the third spiral feature, the first metal line forming a part of each of adjacent spiral features, wherein a gap in the first plane between the first metal line and the second metal line is in a different location than a gap in the second plane between the first metal line and the second metal line such that a length of the first metal line in the first plane is different than a length of the first metal line in the second plane, wherein the first metal line and the second metal line in each of the first spiral feature, the second spiral feature, and the third spiral feature are in a same metallization layer; and a first port extending along a line parallel to the first axis; a second inductor, the second inductor comprising: a second spiral pattern about a second axis, the second axis being parallel to the major surface of the substrate; and a second port extending along a line parallel to the second axis; and a conductive tab electrically coupling the first inductor to the second inductor.
 2. The inductor of claim 1, wherein the first spiral feature, the second spiral feature, and the third spiral feature have a same width.
 3. The inductor of claim 1, wherein the second spiral pattern comprises: a fourth spiral feature in a fourth plane over the substrate; a fifth spiral feature in a fifth plane over the substrate; and a sixth spiral feature in a sixth plane over the substrate, each of the fourth plane, the fifth plane, and the sixth plane being perpendicular to the major surface of the substrate, wherein each of the fourth spiral feature and the fifth spiral feature comprises a third metal line and a fourth metal line discontinuous from the third metal line, the third metal line extending continuously between adjacent spiral features of the fourth spiral feature, the fifth spiral feature, and the sixth spiral feature, the third metal line forming a part of each of adjacent spiral features, wherein a gap in the fourth plane between the third metal line and the fourth metal line is in a different location than a gap in the fifth plane between the third metal line and the fourth metal line such that a length of the third metal line in the fourth plane is different than a length of the third metal line in the fifth plane, wherein the third metal line and the fourth metal line in each of the fourth spiral feature, the fifth spiral feature, and the sixth spiral feature are in the same metallization layer.
 4. The inductor of claim 3, wherein the first metal line and the third metal line are in an uppermost metallization layer of the first inductor and the second inductor.
 5. The inductor of claim 3, wherein the first plane and the fourth plane are a same plane.
 6. The inductor of claim 1, wherein the conductive tab is in an uppermost metallization layer of the first inductor and the second inductor.
 7. The inductor of claim 1, further comprising a connecting metal line coupled directly to the conductive tab.
 8. An inductor comprising: a first inductor, the first inductor comprising: a first coil, the first coil comprising a first plurality of metal features, the first coil rotating around a first axis, the first axis being parallel to a major surface of a substrate, wherein the first coil comprises: a first spiral feature in a first plane over the substrate; a second spiral feature in a second plane over the substrate; and a third spiral feature in a third plane over the substrate, each of the first plane, the second plane, and the third plane being perpendicular to a major surface of the substrate; wherein the first spiral feature and the second spiral feature comprise a first metal line, the first metal line extending in the first plane from a first via and in the second plane to a second via, the first metal line comprising a first interconnect segment extending from the first plane to the second plane; and wherein the second spiral feature and the third spiral feature comprise a second metal line, the second metal line extending in the second plane from a third via and in the third plane to a fourth via, the second metal line comprising a second interconnect segment extending from the second plane to the third plane, the first interconnect segment being positioned at a different location in the first plane than the second interconnect segment is positioned in the second plane such that an axis perpendicular to the first plane intersects the first interconnect segment but not the second interconnect segment, wherein the first metal line and the second metal line are in a same metallization layer; and a first port extending along a line parallel to the first axis; a second inductor, the second inductor comprising: a second coil, the second coil comprising a second plurality of metal features, the second coil rotating around a second axis, the second axis being parallel to the first axis; and a second port extending along a line parallel to the second axis; and a conductive tab electrically coupling the first inductor to the second inductor.
 9. The inductor of claim 8, wherein the second inductor is a mirror image of the first inductor.
 10. The inductor of claim 8, wherein an uppermost metal feature of the first plurality of metal features of the first coil is in a same metallization layer as an uppermost metal feature of the second plurality of metal features of the second coil.
 11. The inductor of claim 10, wherein the conductive tab is in the same metallization layer.
 12. The inductor of claim 11, further comprising a metal line extending away from the conductive tab in a direction parallel to the first axis.
 13. The inductor of claim 8, wherein a width of the first coil in a direction perpendicular to the first axis is a same width as a width of the second coil in a direction perpendicular to the second axis.
 14. The inductor of claim 8, wherein the first coil and the second coil have a same number of spiral features.
 15. An inductor comprising: a first inductor, the first inductor comprising: a first coil, the first coil spiraling around a first axis, the first axis being parallel to a major surface of a substrate; and a first port extending along a first line parallel to the first axis; a second inductor, the second inductor comprising: a second coil, the second coil spiraling around a second axis, the second axis being parallel to the first axis, wherein a pattern of the first coil is a mirror image of a pattern of the second coil, the first coil not overlapping the second coil in a direction parallel to the first axis and the second axis; and a second port extending along a second line parallel to the second axis; and a conductive tab electrically coupling the first inductor to the second inductor; wherein the first coil and the second coil comprises: a first spiral feature in a first plane over the substrate, the first spiral feature comprising a first lower line and a first upper line electrically coupled by a first conductive column; a second spiral feature in a second plane over the substrate, the second spiral feature comprising a second lower line and a second upper line electrically coupled by a second conductive column; and a third spiral feature in a third plane over the substrate, the third spiral feature comprising a third lower line and a third upper line electrically coupled by a third conductive column, each of the first plane, the second plane, and the third plane being perpendicular to a major surface of the substrate; wherein the first upper line extends along the first plane and the second plane, the second upper line extends along the second plane and the third plane; wherein the first upper line is coupled to the second lower line by a fourth conductive column; wherein the second upper line is coupled to the third lower line by a fifth conductive column; and wherein a location of a gap in the second plane between the first upper line and the second upper line is at a different relative location than a location of a gap between the second upper line and the third upper line in the third plane such that an axis perpendicular to the first plane intersects the gap in the second plane but not the gap in the third plane.
 16. The inductor of claim 15, wherein the first lower line, the second lower line and the third lower line are a same length.
 17. The inductor of claim 15, wherein the first conductive column comprises at least one metal pad and a plurality of metal vias.
 18. The inductor of claim 15, wherein the conductive tab is in a same metallization layer as the first port and the second port.
 19. The inductor of claim 15, wherein the first coil has a constant width.
 20. The inductor of claim 19, wherein the second coil has the constant width. 